Meaning: Its source is a Chinese expression meaning "Earth."

Languages: This boy's name is used in Chinese, Hawaiian, Norwegian, Swedish and Danish.

Compound Forms: Kyden

Popularity: The name Kai ranked 323rd in popularity for males of all ages in a sample of 2000-2003 Social Security Administration statistics.

Narrative: Its Scandinavian source is a Greek expression meaning ''Earth.''

In Hawaiian, the name means ''Sea water.''

Depending on the tone and character associated with the name, its Chinese meaning can be ''Victorious,'' ''Open,'' ''Start'' or ''Ideal.''

Meaning: Its source is an English expression meaning "Happy."

Popularity: The name Kai ranked 3378th in popularity for females of all ages in a sample of the 1990 US Census.

Though this name appears on the 1990 U.S. Census lists, it is used by only a small percentage of the general population.

Narrative: Though the male Kay probably comes from the Latin name Gaius, meaning ''happy,'' this female version more likely started as a nickname for names beginning with the letter K, especially Katherine, Karen and Kathryn.